The multiton behemoths traveled up to 11 miles (18 kilometers) from the quarry where most of them were carved, without the benefit of wheels, cranes, or even large animals.

Scientists have tested many ideas in the past, figuring that the islanders must have used a combination of log rollers, ropes, and wooden sledges. Now a pair of archaeologists have come up with a new theory: Perhaps the statues, known as moai, were "engineered to move" upright in a rocking motion, using only manpower and rope.

Watch video: Easter Island statues rocking forward

Terry Hunt of the University of Hawaii and Carl Lipo of California State University Long Beach have worked closely with archaeologist Sergio Rapu, who's part of the South Pacific island's population of indigenous Rapanui, to develop their idea. They've observed that fat bellies allowed the statues to be tilted forward easily, and heavy, D-shaped bases could have allowed handlers to roll and rock the moai side to side.

Last year, in experiments funded by the National Geographic Society's Expeditions Council, Hunt and Lipo showed that as few as 18 people could, with three strong ropes and a bit of practice, easily and relatively quickly maneuver a ten-foot (three-meter), five-ton moai replica a few hundred yards (a few hundred meters). No logs were required. (National Geographic News is a division of the Society.)

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In previous efforts to solve the mystery, Czech engineer Pavel Pavel worked with Norwegian explorer-adventurer Thor Heyerdahl and a team of 17 helpers to propel an upright, 13-foot (4-meter), nine-ton moai forward with twisting motions, keeping the statue fully upright at all times. That was in 1986. But Pavel's team damaged the moai's base and had to stop. (Related: "Easter Island Settled Later, Depleted Quicker Than Thought?")

A year later U.S. archaeologist Charles Love and a team of 25 erected a 13-foot (4-meter), nine-ton model upright on a wooden sledge and moved it over log rollers, advancing it 148 feet (45 meters) in two minutes.

Meanwhile, for many of Easter Island's 2,000 or so indigenous Rapanui, descended from the original Polynesian settlers, the answer is simple. "We know the truth," says Suri Tuki, 25, a tour guide. "The statues walked."